Recent scientific advances demonstrate that for people living with HIV, antiretroviral therapy (ART) is the most effective strategy to improve immune function, reduce morbidity, improve quality of life, prolong survival, and prevent HIV transmission. Translating this knowledge into practice, however, requires prompt diagnosis and linkage to care, entry into care with timely ART initiation, and engagement in care, support for ART adherence, and retention to promote durable virologic suppression. Addressing failures in the implementation of this cascade of care, often referred to as the Seek, Test, Treat, and Retain (STTR) paradigm, is vital to achieving the goals of the National HIV/AIDS strategy in the United States. To date, much of the research and discussion surrounding this strategy has focused on expanding HIV testing to improve the early identification of new cases. There has been less attention focused on linkage to, engagement in, and retention in care. Specifically, little attention has focused on identifying HIV-infected individuals who, despite being aware of their diagnosis, have never been in HIV care, are intermittent users of care, or have dropped out of care. A particularly difficult subpopulation to link to and retain in HIV care are HIV-infected drug users. In Puerto Rico, drug use, especially injection drug use, continues to fuel a fast-growing HIV epidemic. Within this context, the overall goal of our proposed project is to implement and evaluate a community-level, structured approach to enhance HIV care access and retention for drug users in San Juan, Puerto Rico. The proposed intervention will be to: 1) identify drug users living with HIV who either do not know their HIV status and/or are not engaged in HIV care; 2) provide direct HIV care services through a mobile health van; and 3) support identified HIV-infected drug users with patient navigators to enhance their ability to engage in HIV care, to initiate antiretroviral therapy, and maintain adherence to their treatment regimens. We are proposing to evaluate our structural enhanced care approach through a randomized roll-out design, a refinement of the stepped-wedge design. The community-level success of the intervention will be assessed by evaluating virologic suppression (primary biological outcome), increased attendance to HIV care visits, uptake of antiretroviral therapy, adherence to HIV treatment regimens, and decreased substance use (as secondary behavioral outcomes) in an independent cohort of HIV-positive individuals drawn from each of the neighborhoods included in the intervention. We will also evaluate the implementation process and cost of the enhanced care approach including implications for cost-effectiveness, feasibility of expansion, and sustainability.